In a nutshell: Researchers have identified a new type of visual representation in the brain, using modelling and electrophysiological techniques.

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When the brain processes visual information, it breaks each image down into pieces. Each piece is analysed by a different group of brain cells in the visual cortex. The cells that analyse adjacent pieces of the image are next to each other in the brain. This means that what we see is essentially ‘mapped’ onto our visual cortex.

Traditionally, these so-called topographic maps have been classified according to whether they represent visual information as a mirror image or a non-mirror image of what you see. This classification is widely used to determine the transition between areas in the visual cortex.

Now, researchers have identified a third type of map that combines both types of representation within a single area.

Led by Brain Function CoE investigators Marcello Rosa and Elizabeth Zavitz from Monash University, in collaboration with IBM Research, the researchers modelled how topographic maps are formed during brain development. For the first time, they investigated what happens when two maps develop in adjacent areas, which is common in the brain.

The researchers found that some configurations of areas led to a previously unknown, ‘twisted’ type of map, which combines regions that represent images as both mirror images and non-mirror images. Using advanced electrophysiological techniques, they showed that this type of map actually exists in the primate brain.

The primate cortex is separated into dozens of visual areas that form a mosaic of individual visual maps. This study demonstrates that the formation of two adjacent areas can create new types of organization that would not be predicted by modelling the formation of each area independently.

This means that to capture the full complexity of the human brain, it will be necessary for models to incorporate multiple areas of the brain and take into account the fact that they develop at different times.

Next steps:
The team is planning to create a more comprehensive model that incorporates information about the sequence of development of areas across the entire visual cortex. They can then use this model to simulate the formation of maps. This will be important to understand differences in the organisation of the cortex between species, including humans.

Yu, H.-H., Rowley, D. P., Price, N. S. C., Rosa, M. G. P., & Zavitz, E. (2020). A twisted visual field map in the primate dorsomedial cortex predicted by topographic continuity. Science Advances, 6, eaaz8673. doi: 10.1126/sciadv.aaz8673

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